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1
Content available Mixed convection heat transfer of a nanofluid in a square ventilated cavity separated horizontally by a porous layer and discrete heat source
Messaoud Hamdi, Adel Sahi, Ouerdia Ourrad
Archives of Thermodynamics
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2023
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Vol. 44, no 2
87--114
EN
Laminar mixed convection heat transfer in a vented square cavity separated by a porous layer filled with different nanofluids (Fe3O4, Cu, Ag and Al2O3) has been investigated numerically. The governing equations of mixed convection flow for a Newtonian nanofluid are assumed to be two-dimensional, steady and laminar. These equations are solved numerically by using the finite volume technique. The effects of significant parameters such as the Reynolds number (10 ≤ Re ≤ 1000), Grashof number (103 ≤ Gr ≤ 106 ), nanoparticle volume fraction (0.1 ≤ φ ≤ 0.6), porous layer thickness (0 ≤ γ ≤ 1) and porous layer position (0.1 ≤ δ ≤ 0.9) are studied. Numerical simulation details are visualized in terms of streamline, isotherm contours, and average Nusselt number along the heated source. It has been shown that variations in Reynolds and Darcy numbers have an impact on the flow pattern and heat transfer within a cavity. For higher Reynolds (Re > 100), Grashof (Gr > 105 ) numbers and nanoparticles volume fractions the heat transfer rate is enhanced and it is optimal at lower values of Darcy number (Da = 10−5 ). In addition, it is noticed that the porous layer thickness and location have a significant effect on the control of the heat transfer rate inside the cavity. Furthermore, it is worth noticing that Ag nanoparticles presented the largest heated transfer rate compared to other nanoparticles.
2
Content available remote Effects of Hindrance Factors on a Squeeze Film of a Porous Bearing Lubricated With a Dehaven Fluid
Walicka A., Walicki E., Jurczak P., Falicki J.
Machine Dynamics Research
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2018
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Vol. 42, No. 1
15--33
EN
In the paper the influence of the hindrance factors on the pressure distribution and loadcarrying capacity of a curvilinear thrust porous bearing is discussed. The equations of motion of a pseudo-plastic fluid of DeHaven are used to derive the Reynolds equation. The general considerations on the flow in a bearing clearance were presented. The analytical considerations on the flow in a thin porous layer composed of capillaries were also presented. Two models of the porous region were used, e.g.: capillary tube with constant cross-section and capillary tube with variable cross-section with rectilinear generatrices. Next, using the Morgan-Cameron approximation the modified Reynolds equation was obtained. As a result the formulae expressing pressure distribution and load-carrying capacity were obtained. Thrust radial bearing with a squeeze film of DeHaven fluid was considered as an example.
3
Content available Simulation of the flow through porous layers composed of converging-diverging capillary fissures or tubes
Walicka A.
International Journal of Applied Mechanics and Engineering
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2018
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Vol. 23, no. 1
161--185
EN
In this paper, a porous medium is modelled by a network of converging-diverging capillaries which may be considered as fissures or tubes. This model makes it necessary to consider flows through capillary fissures or tubes. Therefore an analytical method for deriving the relationships between pressure drops, volumetric flow rates and velocities for the following fluids: Newtonian, polar, power-law, pseudoplastic (DeHaven and Sisko types) and Shulmanian, was developed. Next, considerations on the models of pore network for Newtonian and non-Newtonian fluids were presented. The models, similar to the schemes of central finite differences may provide a good basis for transforming the governing equations of a flow through the porous medium into a set of linear or quasi-linear algebraic equations. It was shown that the some coefficients in these algebraic equations depend on the kind of the capillary convergence.
4
Content available Influence of wall porosity and surfaces roughness on the steady performance of an externally pressurized hydrostatic conical bearing lubricated by a Rabinowitsch fluid
Walicka A., Walicki E., Jurczak P., Falicki J.
International Journal of Applied Mechanics and Engineering
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2017
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Vol. 22, no. 3
717--737
EN
In the paper, the influence of both the bearing surfaces roughness as well as porosity of one bearing surface on the pressure distribution and load-carrying capacity of a curvilinear, externally pressurized, thrust bearing is discussed. The equations of motion of a pseudo-plastic Rabinowitsch fluid are used to derive the Reynolds equation. After general considerations on the flow in a bearing clearance and in a porous layer using the Morgan-Cameron approximation and Christensen theory of hydrodynamic lubrication with rough bearing surfaces the modified Reynolds equation is obtained. The analytical solution is presented; as a result one obtains the formulae expressing the pressure distribution and load-carrying capacity. Thrust radial and conical bearings, externally pressurized, are considered as numerical examples.
5
Content available Curvilinear squeeze film bearing with porous wall lubricated by a Rabinowitsch fluid
Walicka A., Walicki E., Jurczak P., Falicki J.
International Journal of Applied Mechanics and Engineering
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2017
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Vol. 22, no. 2
427--441
EN
The present theoretical analysis is to investigate the effect of non-Newtonian lubricant modelled by a Rabinowitsch fluid on the performance of a curvilinear squeeze film bearing with one porous wall. The equations of motion of a Rabinowitsch fluid are used to derive the Reynolds equation. After general considerations on the flow in a bearing clearance and in a porous layer using the Morgan-Cameron approximation the modified Reynolds equation is obtained. The analytical solution of this equation for the case of a squeeze film bearing is presented. As a result one obtains the formulae expressing pressure distribution and load-carrying capacity. Thrust radial bearing and spherical bearing with a squeeze film are considered as numerical examples.
6
Content available Thrust porous bearing with rough surfaces lubricated by a rotem-shinnar fluid
Walicka A., Walicki E.
Acta Mechanica et Automatica
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2016
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Vol. 10, no. 1
50--55
EN
In the paper the influence of both bearing surfaces roughness and porosity of one bearing surface on the pressure distribution and load-carrying capacity of a thrust bearing surfaces is discussed. The equations of motion of a pseudo-plastic fluid of Rotem-Shinnar, are used to derive the Reynolds equation. After general considerations on the flow in a bearing clearance and in a porous layer using the Morgan-Cameron approximation and Christensen theory of hydrodynamic lubrication the modified Reynolds equation is obtained. The analytical solutions of this equation for the cases of squeeze film bearing and externally pressurized bearing are presented. As a result one obtains the formulae expressing pressure distribution and load-carrying capacity. Thrust radial bearing with squeezed film is considered as a numerical example.
7
Content available Wytwarzanie warstw porowatych przy użyciu mikrospawania
Depczyński W., Młynarczyk P., Spadło S., Ziach E.
TTS Technika Transportu Szynowego
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2015
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R. 22, nr 12
378--380, CD
PL
Celem pracy było zapoznanie się z metodą mikrospawania opornościowo-impulsowego oraz zaznajomienie się z właściwościami i mikrostrukturą porowatych warstw wierzchnich. Został również dokonany dobór materiału podłoża stali S235JR oraz materiałów napawanych, którymi były pa-sty wykonane z oleju silikonowego oraz mieszanin proszków żelaza: NC 100.24, ASC 100.29, Distaloy SE z tlenkiem żelaza (Fe2O3) i miedzią (Cu). Po przygotowaniu materiałów nastąpił dobór właściwych parametrów mikrospawania. W celu wytworzenia porowatej warstwy wierzchniej na stali zastosowano napawanie metodą mikrospawania opornościowo-impulsowego z wykorzystaniem urządzenia do mikrospawania WS7000S firmy SST France & Vision Lasertechnik.
EN
The aim of this study was to examine method of resistance microwelding and familiarization with the properties and microstructure of porous surface layers made using this method. The selection of the substrate material (S235JR steel) and welded materials, which were pastes made of silicone oil and iron powders (NC 100.24, ASC 100.29, Distaloy SE) with Fe2O3 and Cu powders addition was made. After selecting the materials the choice of appropriate microwelding parameters was made.
8
Content available Porous squeeze film bearing with rough surfaces lubricated by a Bingham fluid
Walicka A., Walicki E., Jurczak P., Falicki J.
International Journal of Applied Mechanics and Engineering
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2014
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Vol. 19, no. 4
795--808
EN
In the paper the effect of both bearing surfaces and the porosity of one bearing surface on the pressure distribution and load-carrying capacity of a squeeze film bearing is discussed. The equations of motion of a Bingham fluid in a bearing clearance and in a porous layer are presented. Using the Morgan-Cameron approximation and Christensen theory of rough lubrication the modified Reynolds equation is obtained. The analytical solutions of this equation for a squeeze film bearing are presented. As a result one obtains the formulae expressing pressure distribution and load-carrying capacity. A thrust radial bearing is considered as a numerical example.
9
Określenie skuteczności odpylania polidyspersyjnej warstwy porowatej na podstawie wybranego modelu filtracji
Rybarczyk A., Raczkowski P.
Zeszyty Naukowe. Mechanika / Politechnika Opolska
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2008
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Vol. 324, z. 90
49-58
PL
W artykule przedstawiono wyniki obliczeń skuteczności odpylania gazów w warstwie porowatej zbudowanej ze żwiru przy wykorzystaniu istniejącego modelu filtracji. Do obliczeń przyjęto rzeczywiste parametry złoża i procesu filtracji zastosowane w projektowaniu odpylacza nasypowego. Przeprowadzono analizę procesu odpylania wykazując, że przyjęty model obowiązuje jedynie dla parametrów, jakie zastosowano w procesie jego tworzenia. Wyniki analizy przedstawiono w tabelach i na wykresach.
EN
In the paper is presented the results of calculations of dust extraction effectiveness in porous layer which is build from slag using existing model of filtration. The real parameters of filter bed and filtration process were applied in projecting of the graver filter. The analyze of dust extraction process was showed that used model is in force only for parameters which was applied in process of its creating. Analyses are presented in schedules and on graphs.
10
Content available remote Rotational inertia effect in a curvilinear thrust bearing with porous layer lubricated by a Newtonian fluid
Jurczak P.
International Journal of Applied Mechanics and Engineering
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2007
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Vol. 12, no 1
37-45
EN
The flow of a Newtonian lubricant in a bearing clearance is discussed. The bearing is modelled by two rotational surfaces and the porous layer is adhered to the curved impermeable surface. The effects of rotational inertia forces on the pressure distribution are examined. The flow in the bearing clearance is considered with inertia and the Navier-Stokes and Poisson equations are uncoupled by using the Morgan-Cameron approximation. As an example the bearing modelled by two spherical surfaces was discussed in detail.
11
Content available remote Pressure distribution in a squeeze film biobearing lubricated by a synovial fluid
Jurczak P.
International Journal of Applied Mechanics and Engineering
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2006
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Vol. 11, no 4
857-864
EN
The flow of a synovial fluid in a squeeze film biological bearing is considered. The biobearing is modelled by two rotational surfaces and the porous layer is adheres to the curved non-porous surface. The flow in the biobearing clearance is considered with inertia and the Navier-Stokes and Poisson equations are uncoupled by using the Morgan-Cameron approximation. As an example the biobearing modelled by two disks and two spherical surfaces is discussed.
12
Content available remote Onset of convection in a sparsely packed porous layer with throughflow
Shivakumara I. S., Nanjundappa C. E.
Archives of Mechanics
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2001
|
Vol. 53, nr 3
219-241
EN
The onset of Rayleigh-Bénard convection in a sparsely packed porous layer with vertical throughflow is investigated using Brinkman's modification of the Darcy flow model with fluid viscosity different from effective viscosity. The critical Rayleigh numbers are obtained for free-free, rigid-rigid and rigid-free boundaries which are insulated to temperature perturbations. It is noted that an increase in the value of viscosity ratio is to delay the onset of convection. Further, it is observed that the throughflow can be used either to suppress or augment convection, depending on the nature of boundaries and also on the values of physical parameters.
13
Influence of vibrations on diffusive transport of chemicals in saturated porous media
Kondrat V., Kubik J., Czaplia Y.
Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska
|
1999
|
z. 9
111-116
EN
A model which explains the diffusive transport of chemicals in saturated porous media due to vibrations have been developed taking into account restructuring of surface liquid layers. Estimation of effective diffusive coefficient under given vibration parameters is proposed for stratum of pores which are parallel slots of width distributed according to law with a given normal probability density.
PL
W pracy analizuje się zwiększenie szybkości dyfuzji substancji w nasyconym ośrodku porowatym pod wpływem drgań mechanicznych, wywołujących zmianę struktury cieczy związanej z porowatym szkieletem. Dla procesu stacjonarnego wyznacza się efektywne makroskopowe współczynniki dyfuzji substancji, która migruje przez szczeliny płaskiej warstwy zanurzonej w roztworze, przy oddziałaniu harmoniczne zmiennych drgań.
14
Content available remote Obliczeniowe i doświadczalne określenie wartości współczynnika oporu ζ warstwy porowatej złożonej z kulek
Adamowicz K.
Zeszyty Naukowe. Cieplne Maszyny Przepływowe - Turbomachinery / Politechnika Łódzka
|
1999
|
nr 114
19--26
PL
Wielostopniowe rozprężanie w zaworach regulacyjnych pracujących przy wysokich parametrach czynnika, jest sposobem na obniżenie poziomu hałasu emitowanego przez zawory. W tym celu, zamiast klasycznego rozwiązania gniazdo-grzyb, w korpusach zaworów instaluje się zespoły dławiące w postaci kaskad, labiryntów lub warstwy porowatej. W artykule omówiono metody obliczeń współczynnika oporu warstwy porowatej i wyniki badań laboratoryjnych tej warstwy. Przedstawione materiały są fragmentem prac prowadzonych w Instytucie Techniki Cieplnej w Łodzi.
EN
In order to decrease noise level in control valves, multistage expanding of high parameter working medium is used Instead of classical solution with pin and seat, special throttling units in valve casing are mounted. They are in the form of cascades, labyrinths or porous layer. In this article, calculation method of coefficient of resistance of porous layer was described as well as results of laboratory investigations. All presented materials are only a part of works carried out in our Institute of Heat Engineering.
15
Polymer insert of hip joint cup endoprosthesis with modified friction surface
Tsvetkova E., Kadolich Z., Pinchuk L.
Applied Mechanics and Engineering
|
1999
|
Vol. 4, no spec.
247-250
EN
The structural and morphological research of a material friction surface of ultra high molecular weight polyethylene for its use in hip joint cup endoprosthesis has been performed. The dependence of tribotechnical performances of the insert microporous material on parameters of charge state and kind of lubricating liquid has been studied.
16
Onset of convection in an inclined porous layer with anisotropic permeability
Storesletten l., Tveitereid M.
Applied Mechanics and Engineering
|
1999
|
Vol. 4, no 3
575-587
EN
The present paper is concerned with the onset of Rayleigh-Bénard convection in an inclined porous layer with anisotropic permeability. Due to the temperature gradient and the inclination, a steady shear flow is set up. The critical Rayleigh number at marginal stability of this basic flow is calculated and the flow pattern occurring at convection onset is examined. It turns out that anisotropy in the permeability and the shear flow have an essential influence on the selected flow structure. Depending on the anisotropy ratio and the tilt angle, convection rolls are found either with axes parallel to the basic flow or with axes perpendicular to the flow.
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